Ignition and excitation circuit for single-anode pool-type discharge vessels



Sept. 12, 1961 L. FILBERICH 2,999,961

IGNITION AND EXCITATION CIRCUIT FOR SINGLE-ANODE POOL-TYPE DISCHARGE wIssELs Filed 001;. 21, 1959 Jn ven f0 7: 1240;;

United States Patent 0 2,999,961 IGNITION AND EXCITATION CIRCUIT FOR SIN- GLE-ANODE POOL-TYPE DISCHARGE VESSELS Ludwig Filberich, Berlin-Siemensstadt, Germany, assignor to Siemens-Schuckertwerke Aktiengeseilschaft, Berlin- Siemensstadt, Germany, a corporation of Germany Filed Oct. 21, 1959, Ser. No. 847,794 Claims priority, application Germany Nov. 5, 1958 Claims. (Cl. 315--168) My invention relates to single-anode pool-type discharge vessels which, aside from their main anode, comprise an ignitor as well as an exciting or holding anode continuously excited during operation of the tube of the vessel to keep the cathode spot alive after the ignitor pulse is spent.

In power current rectifier vessels of this type the excitation tends to extinguish in the event of high overloads; and it is an object of my invention to prevent the operation of the discharge vessel from being interrupted by such extinction.

According to the invention 1 provide the vessel with ignition control means which, in response to vanishing of the excitation current due to extinction of the excitation arc, produce an ignition pulse and apply it to the ignitor prior to commencement of the next current-conducting cycle period of the vessel. As a result the extinction of the continuous excitation, generally, does not interrupt the rectifying operation of the discharge vessel. For reigniting the excitation are, a time interval of approximately one-half of the alternating main-anode voltage of the vessel is available because any extinction of the continuous excitation are, as a rule, occurs at the end of a current conducting period.

According to a more specific feature of my invention, the ignitor or ignition pin of the vessel is connected with an electric energy storing member through a normally closed contact of a rapidly acting relay whose control winding is connected in the circuit of the excitation anode. While in principle any reactive circuit component is suitable as energy storer, it is preferable to use for this purpose a capacitor which is kept charged during normal operation of the rectifier vessel. In this case, the ignitor circuit is preferably provided with a normally open contact of a relay whose control winding is excited by the capacitor voltage and which drops off instantaneously after discharging of the capacitor while picking up with delay when the capacitor is being charged. By virtue of the delayed pickup of the relay, a suflicient interval of time is available for the capacitor to accumulate the electric charge needed for ignition when starting the tube operation or after an unsuccessful ignition attempt.

According to another, preferred feature of the invention, the primary winding of a transformer is connected in the circuit of the excitation anode and has its secondary winding connected with the ignitor circuit for energizing the latter. By virtue of this circuitry, the vanishing of the excitation current produces in the transformer secondary winding an ignition pulse without requiring the response of any relays. The ignition of the discharge vessel when starting its operation or after unsuccessful attempts at re-ignition is preferably effected by connecting parallel to the continuous excitation gap of the discharge vessel a normally closed contact of a relay which opens with delay when a current starts flowing in the transformer primary winding. Consequently, a primary current can flow through the transformer through the normally closed contact of the latter relay as long as the excitation arc of the vessel is extinct. When the latter relay picks up, the primary current is interrupted, thus inducing an ignition pulse in the secondary winding.

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Due to the delayed response of the relay to the occurrence of current in the primary winding, a suflicient magnetic excitation of the transformer is built up before the primary current is interrupted.

According to a further feature, the relay to be energized in dependence upon the primary current of a transformer, has its coil circuit controlled by a normally closed contact of a control relay whose winding is connected in series with the primary winding of the transformer.

The invention will be further described with reference to the embodiments of tube ignition and excitation networks illustrated by way of example in FIGS. 1 and 2 respectively of the accompanying drawing.

The single-anode mercury pool rectifier tube 1, schematically shown in both illustrations, comprises a main anode 2, a control grid 3, an excitation or holding anode 4, a pool cathode 5, and an ignitor or ignition pin 6.

According to FIG. 1, a transformer 10 with a primary winding 11 and two secondary windings 12 and 13 is provided for supplying continuous excitation to the excitation anode 4 and energizing the ignition circuit of ignitor 6. The primary winding 11 is connected to an alternating-voltage source at terminals 9. The voltage of secondary winding 13 is rectified by a dry-rectifier bridge network 14 Whose positive output terminal is connected with the excitation anode 4 through an adjustable resistor 15, the control winding of a relay 16 and a smoothing reactor 17, a smoothing capacitor 18 being connected across the rectifier output leads between resistor 15 and reactor coil 17. The negative output terminal of rectifier bridge 14 is connected to the cathode 5 of tube 1.

The secondary winding 12 furnishes the energy required for ignition of the tube. The voltage of winding 12 is rectified by a dry-rectifier bridge network 20. Connected across the two output leads of rectifier bridge 29 is a capacitor 21 in series with a resistor 22. The capacitor is normally kept charged to serve as energy storer. Connected parallel to capacitor 21 is the control winding of a relay 23 in series with a resistor 24. Another capacitor 25 lies in parallel to the winding of relay 23, and a diode 26, preferably of the solid-state type, is con nected parallel to the resistor 24. The RC member constituted by components 24 and 25 causes the relay 23 to pick up with delay when the capacitor 21 is being charged. However, the relay 23 drops off instantaneously when capacitor 21 discharges because the discharge occurs through the diode 26 virtually without delay.

A positive terminal of capacitor 21 is connected with ignitor 6 through a normally open contact 23a of relay 23 and a normally closed contact 16a of relay 16 in series with a diode 27 preferably of the solid-state type. The negative terminal of capacitor 21 is directly connected with the tube cathode 5.

The device according to FIG. 1 operates as follows:

In the inactive condition of the rectifier tube 1, the contact 16a is closed and the contact 23 is open, the arrows shown at the respective contacts indicating the drop-off direction of the relays 16 and 23. When the alternating voltage at terminals 9 is switched on, the capacitor 21 is charged. When the capacitor 21 has accumulated a given charging quantity, the relay 23 will respond and close its contact 23a. Now the capacitor 21 discharges through the ignitor pin 6 so that an arc discharge in tube 1 between excitation anode 4 and cathode 5 commences. Immediately upon ignition, the relay 23 drops off and opens its contact 23a. Due to the flow of excitation current, the relay 16 picks up and opens contact 16a. The capacitor 21 is now again charged, with contact 23 being open. As soon as the capacitor has reached a given voltage, the relay 23 again picks up and closes the contact 23a. Since now the contact 16a is open, the capacitor 21 remains charged as long as the operation of tube 1 continues without trouble.

If the continuous direct-current are at excitation anode 4 becomes extinguished during operation of tube 1, the rapid relay 16 drops 013? after an interval of time much smaller than one-half-cycle period of the energizing alternating voltage, this interval being in the order of a few milli-seconds. Hence, contact 16a closes so that capacitor 21 discharges through the ignitor 6. In general, the continuous excitation of anode 4 is immediately re-established so that the rectifier tube is again in operating condition for the next current-conducting period. The further operations are the same as described above. However, if the ignition is not successful, the capacitor is again charged, whereafter the contact 23a closes and initiates another ignition attempt.

In the embodiment of FIG. 2, the continuous excitation current supplied from the dry-rectifier bridge network 3%) passes through the primary winding 31 of a transformer whose secondary winding 32 is connected in the ignitor circuit. The circuit of the excitation anode 4 further comprises a relay 33 with a normally open contact 33a. A normally closed contact 35a of another relay 35 is connected in parallel to the continuous excitation gap between components 4 and of tube 1. Contact 35a is designed as a vacuum switch; that is, it is enclosed within an evacuated envelope. The control coil of relay 35 is connected in series with the normally open contact 33a of relay 33 and in parallel with the capacitor 36 of an RC member also comprising a resistor 37, so that relay 35 responds with delay upon closing of contact 33a.

A device according to FIG. 2 operates as follows:

In the inactive condition of the rectifier tube, contact 33a is open and contact 35a is closed as shown. After voltage from source 9 is switched on, a current first flows through the control coil of relay 33, the primary winding 31, and the contact 35a. This current causes relay 33 to pick up. Contact 33a closes and energizes the relay 35 which picks up after lapse of a delaying interval determined by the dimensioning of the circuit components 36 and 37. Relay 35 then opens its contact 35a, thus interrupting the current flowing through the primary winding 31. The rapid change in current induces in the secondary winding 32 a high peak voltage which drives a current pulse through the ignitor pin 6 of the tube 1. As long as the tube 1 continues operating without trouble, contact 33a remains closed and contact 35a open.

When the excitation are between anode 4' and cathode 5 tears 01$, for example due to overloading of the rectifier tube, the rapid current change in winding 31 induces a high voltage peak in secondary winding 32, thus causing a current pulse to pass through the ignitor 6 of the tube. This immediately ignites the tube 1 without any relay being required to respond. Only if such rapid ignition fails, will the relay 33 drop off in order to cooperate with the time-delay relay 35 in initiating a periodic supply of pulses to the ignitor 6 for restarting the tube.

It will be obvious to those skilled in the art, upon studying this disclosure, that my invention permits of various modifications, such as the substitution of the above-described contact relays by electronic switches, for example tubes or transistors, and hence may be given embodiments other than particularly illustrated and described herein, without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim:

1. With a single-anode discharge vessel having a pool cathode, a main anode, an ignitor and an excitation anode, the combination of an ignition and excitation system comprising a pulse circuit connected between said cathode and said ignitor and having pulse generating means for supplying an ignition pulse to said ignitor, an excitation circuit connected between said cathode and said excitation anode and having continuous-current supply means, an electric energy storer and a direct-current source connected thereto for normally maintaining said storer in changed condition, and control circuit means connected with said excitation circuit and responsive to current change in said excitation circuit, said control circuit means connecting said energy storer to said pulse circuit for issuing an ignition pulse from said storer to said ignitor, whereby the moment of said pulse is dependent upon the vanishing moment of excitation current and independent of the phase condition of the discharge vessel to re-ignite said excitation prior to the next conducting halfcycle period of said vessel.

2. With a single-anode discharge vessel having a pool cathode, a main anode, an ignitor and an excitation anode, the combination of an ignition and excitation system comprising a pulse circuit connected between said cathode and said ignitor, an excitation circuit connected between said cathode and said excitation anode and having continuouscurrent supply means, an electric energy storer and a voltage source connected thereto for normally maintaining said storer in charged condition, normally open relay means connecting said storer with said ignition circuit and having a zero-current responsive control circuit connected with said excitation circuit, said relay means having a time constant smaller than one-half-cycle period of said discharge vessel, whereby vanishing of excitation current causes closing of said relay means to discharge an ignition pulse from said storer to said ignitor at a moment independent of the phase condition of the discharge vessel and prior to the next conducting half-cycle period of said vessel.

3. With a single-anode discharge vessel having a pool cathode, a main anode, an ignitor and an excitation anode, the combination of an ignition and excitation system comprising a pulse circuit connected between said cathode and said ignitor, an excitation circuit connected between said cathode and said exciter anode and having continuous-current supply means, a capacitor and a voltage source connected thereto for normally maintaining said capacitor charged, normally open relay means connecting said capacitor With said ignition circuit and having a zero-current responsive control circuit connected with said excitation circuit, said relay means having a time constant smaller than one-half-cycle period of said discharge vessel, whereby vanishing of excitation current causes closing of said relay means to discharge an ignition pulse from said capacitor to said ignitor at a moment independent of the phase condition of the discharge vessel and prior to the next conducting half-cycle period of said vessel.

4. With a single-anode discharge vessel having a pool cathode, a main anode, .an ignitor and an excitation anode, the combination of an ignition and excitation system comprising a pulse circuit connected between said cathode and said ignitor, an excitation circuit connected between said cathode and said excitation anode and having continuous-current supply means, an electric energy storer and a voltage source connected thereto for normally maintaining said storer in charged condition, a rapid electromagnetic relay having a normally closed contact connecting said storer with said ignition circuit and having a relay coil connected in said excitation circuit to be energized by current flowing in said excitation circuit so that said contact is open during normal operation of said vessel, said relay having a time constant smaller than one-half-cycle period of said discharge vessel, whereby vanishing of excitation current causes said contact to discharge from said storer an ignition pulse to said ignitor prior to the next conducting half-cycle period of said vessel.

5. With a single-anode discharge vessel having a pool cathode, a main anode, an ignitor and an excitation anode, the combination of an ignition and excitation system comprising a pulse circuit connected between said cathode and said ignitor, an excitation circuit connected beiWl Said cathode and said exciter anode and having continuous-current supply means, a capacitor and a voltage source connected thereto for normally maintaing said capacitor in charged condition, a rapid electromagnetic relay having a normally closed contact connecting said capacitor with said pulse circuit and having a relay coil connected in said excitation circuit to be energized by current flowing in said excitation circuit so that said contact is open during normal operation of said vessel, whereby vanishing of excitation current causes said contact to discharge from said storer an ignition pulse to said ignitor at a moment independent of the phase condition of the discharge vessel.

6. With a single-anode discharge vessel having a pool cathode, a main anode, an ignitor and an excitation anode, the combination of an ignition and excitation system comprising a pulse circuit connected between said cathode and said ignitor, an excitation circuit connected between said cathode and said exciter anode and having direct-current supply means normally of substantially constant voltage, a transformer having a primary winding connected in said excitation circuit and having a secondary winding connected in said pulse circuit for generating therein an ignition pulse in response to vanishing of excitation current at a moment independent of the phase condition of the discharge vessel.

7. An ignition and excitation system according to claim 6, comprising normally-on switch means connected across said excitation anode and cathode and having timedelay control means responsive to current flowing in said primary winding so as to be switched off with delay upon commencement of current flow in said primary winding.

8. An ignition and excitation system according to claim 6, comprising an electromagnetic relay having a normally closed contact connected across said excitation anode and cathode and having a coil circuit for controlling said contact, and time-delay control means connected with said excitation circuit for energizing said coil circuit in delayed response to commencement of current flow in said primary winding.

9. An ignition and excitation system according to claim 6, comprising a first electromagnetic relay having a normally closed contact connected across said excitation anode and cathode and having a coil circuit for controlling said contact, and a second electromagnetic relay having a normally open contact in said coil circuit and a control coil connected in said excitation circuit, and time delay means connected with one of said relays, whereby said first-relay contact is opened a given interval of time upon commencement of current flow in said primary winding.

10. An ignition and excitation control system according to claim 5, comprising another electromagnetic relay having a normally open contact connected in said pulse circuit in series with said normally closed contact and having a relay coil for controlling said normally open contact, a resistor connected in series with said coil across said capacitor, and a diode connected parallel to said resistor for delayed closing and undelayed opening of said normally open contact in response to charging and discharging respectively of said capacitor.

References Cited in the file of this patent UNITED STATES PATENTS 1,957,205 Garman May 1, 1934 1,959,201 Frondt May 15, 1934 2,491,990 Longini Dec. 20, 1949 2,535,698 Schmidt Dec. 26, 1950 

